Rubber Cure Time and Press Cost Calculator
Cure time is the largest block of press time on most molded rubber parts, and it is the number an estimator most often guesses. This calculator scales a known cure to a new thickness and temperature, builds the full cycle and prices the press time per part.
Your numbers
Proven cure time for a reference part, from a rheometer-based trial or production history.
Your results
Planning model only. The 10 C doubling rule and thickness exponents are approximations; real cure depends on compound, cure system and part geometry. Confirm with a rheometer cure curve (ASTM D5289) and trial cures. Higher temperature can cause scorch or porosity.
Conversion cost per part vs mold temperature
Sweeps New mold temperature from 150 to 200, holding your other inputs fixed.
Compare quoted and actual press cycles
Optional: we can look at how your quoted cure and cycle times compare with real press data in your ERP or MES.
Optional. The tool and every export work without this. No spam.
How to use it
Start with a reference part where you trust the cure time, then enter its thickness and mold temperature. Enter the new part's thickness and temperature, the handling time to load, close, open and unload, cavities, and your press and labor rates. The primary outputs are estimated cure time and conversion cost per part. Use the chart to see how much temperature really buys you before scorch risk bites.
- Pick the thickness exponent from experience: thin parts near 1, heavy sections near 2.
- Handling time often exceeds 30 seconds even on small molds.
- Use a realistic efficiency that includes mold changes and warm-up.
Method and assumptions
Two scalings are combined. Heat soaks into the part roughly with thickness, ranging from linear for thin sheets to squared for thick sections where conduction dominates, so cure time scales by (new thickness over reference thickness) raised to the chosen exponent. Cure chemistry speeds up with temperature, and the common 10 degree rule of thumb, derived from Arrhenius behavior, halves the time for every 10 C rise. Cycle time is cure plus handling, and cost per part is hourly cost divided by good parts per hour.
Reading the results
With the defaults, a 6 mm part cured in 240 seconds at 170 C becomes a 10 mm part at 180 C needing roughly 150 seconds of cure by this model, about a 3.5 minute cycle once handling is added, which at 12 cavities lands near 190 parts per hour. When the cure share of cycle is above 70 percent, temperature and cure-system changes pay off; below 50 percent, look at loading automation and mold design first.
Common mistakes
The biggest error is raising temperature without checking scorch safety, flow time and bond or surface quality. Others include costing a press at nameplate capacity instead of real efficiency, forgetting post-cure ovens for silicone and fluoroelastomer, and applying a rule of thumb to a compound with a very different cure system. Treat the number as a quoting estimate and then lock the real cure on the first sample.
Frequently Asked Questions
What is the 10 degree rule for rubber cure?
It is a rule of thumb that cure rate about doubles for each 10 C rise in temperature, so cure time halves. It comes from Arrhenius-type kinetics and works within a limited range. Real compounds vary, and scorch limits cap how hot you can go.
Why does thickness raise cure time so much?
Rubber is a poor heat conductor, so the center of a thick part lags the mold surface. Thin parts follow thickness roughly linearly, while thick sections approach a squared relationship because heat conduction controls the cure.
How do I find the real cure time?
Run a rheometer cure curve per ASTM D5289 or ISO 6502 and read t90 at mold temperature, then add allowance for heat-up on thick parts. Confirm with trial cures and check hardness, compression set and appearance.
Does post-cure belong in this calculator?
No. Post-cure ovens, common for silicone, FKM and some EPDM seals, are a separate batch step. Cost them separately by oven hours and load size, then add them to the quote worksheet as a secondary operation.
If your shop tracks press cycles in an MES or ERP, Netray can help compare quoted cure times with actual cycle data and flag drifting jobs. Ask for a short review of your cycle data.
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